Daidzein is an isoflavone, which is a hormone-like substance found in soybeans. Daidzein is the second most plentiful isoflavone in soy, after genistein. Numerous studies have shown that, like genistein, daidzein is both a phytoestrogen and antioxidant, and it is most often used to treat conditions affected by an estrogen levels in the body.

Daidzein inhibits the growth of cancer by taking the place of estrogen on receptors in cancerous cells that need estrogen to grow. Daidzein also inhibits the growth of tumors by forcing cells to differentiate normally, rather than the wild, exponential cell growth seen in tumor cells. Daidzein has been shown to be especially effecting in checking the growth of leukemia cells and melanoma cells.

As a phytoestrogen, daidzein mimics the effects of estrogen in the body, and may be a useful treatment for conditions caused or worsened by declining estrogen levels during menopause, including osteoporosis and increased risk of heart disease. Soy isoflavones have demonstrated an ability to lower low-density lipoprotein (LDL, or “bad”) cholesterol levels, and to help prevent plaque build-up in the arteries. It has also been suggested that soy isoflavones may be useful for treatment of Alzheimer’s disease by preventing a build-up of plaque in blood vessels in the brain.

You can get more daidzein in your diet by eating foods made from soybeans or the soybeans themselves. Tofu, soy milk, soy flour, miso, and roasted soybeans are all good sources of isoflavones. There are also isoflavone supplements on the market containing significant amounts of daidzein and genistein, another anti-cancer phytoestrogen found in soy. You can also get a good amount of isoflavones from herbal kudzu supplements—kudzu contains soy isoflavones.

People concerned with osteoporosis may want to try ipriflavone, a supplement containing a chemically altered form of soy isoflavones, which has been proven the most effective isoflavone supplement for preventing bone loss.

There is no recommended dosage for daidzein, although the average daily intake of isoflavones in Japan is about 200 milligrams. There have been no toxic side effects associated with daidzein, but because it is a phytoestrogen, there has been some concern that it could actually stimulate the growth of estrogen-stimulated cancers or interfere with the action of birth control pills. Men and women diagnosed with estrogen-related cancers should not consume isoflavones, as there is some research that suggests that genistein and daidzein may aggravate these conditions.

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